SECRETARY'S REPORT 87 



cromeleoritic dust particles have been chemically analyzed and their 

 composition compared with that of small magnetic particles collected 

 in the vicinity of the Canyon Diablo and Sikhote-Alin meteoritic 

 craters. This research contributes to our understanding of the inter- 

 planetary medium. 



The electron- probe microanalyzer designed and developed by Dr. 

 F. Behn Kiggs, Jr., allows the chemical analysis of a meteorite speci- 

 men w'ithout destruction of the sample. It is being used to measure 

 the concentrations of iron, nickel, and cobalt in magnetic particles 

 that are assumed to be micrometeorites, ranging in diameter from 50 

 to 1,000 microns. Particles of similar appearance are found to show 

 a wide range of chemical content. Nickel concentrations up to 5 per- 

 cent have been found in most of the particles analyzed. This re- 

 search will provide more information on the history and mode of 

 formation of meteorites. 



Dr. Riggs designed and built a simple, hand-operated, scamiing 

 spectrometer which makes it possible to measure the elements in 

 the surface of a sample more rapidly than with fixed-channel 

 spectrometers. 



Jerald P. Annese, with Dr. D. W. Batteau (formerly at Harvard 

 University), designed and developed an emission-current regulating 

 system for the electron-probe microanalyzer, which increases the 

 accuracy of the analyzer. 



Dr. Fireman is contmuing his measurement of radioactive isotopes 

 in meteorites. The resulting data provide basic information on the 

 distribution, intensity, and constancy of cosmic rays in space, and 

 indicate the probable age and original mass of specific meteorites 

 found on earth. The time of solidification and the composition of the 

 primordial gas in meteorites are important problems in the histoiy of 

 the solar system. By radiochemical methods. Dr. Fireman completed 

 the measurements on the Aroos and Bruderheim meteorites, and has 

 derived an estimate of the potassium-argon age of the Canyon Diablo 

 meteorite. To increase the value of these techniques, Dr. Fireman has 

 urged the establishment of a large-scale program for the discovery 

 of freshly fallen meteorites. 



Dr. Richard E. McCrosky began plans for implementing such a 

 program, to locate and recover meteorites as soon as possible after 

 their fall, by photographing meteors in flight and analyzing the 

 photographic records to find the place of fall. The program will 

 also augment our knowledge of the numbers, masses, and orbits of 

 meteors. 



In collaboration with scientists of the Harvard College Observatory, 

 the U.S. Air Force, the Lincoln Laboratories of the Massachusetts 

 Institute of Technology, and the New Mexico College of Agriculture 



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